AudioMixerPlatformAudioUnit.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "AudioMixer.h"
#include "DSP/Dsp.h"
#include <AudioToolbox/AudioToolbox.h>
#include <AudioUnit/AudioUnit.h>
 
// Any platform defines
namespace Audio
{
    
    class FMixerPlatformAudioUnit : public IAudioMixerPlatformInterface
    {
        
    public:
        
        FMixerPlatformAudioUnit();
        ~FMixerPlatformAudioUnit();
        
        //~ Begin IAudioMixerPlatformInterface
        virtual FString GetPlatformApi() const override { return TEXT("AudioUnit"); }
        virtual bool InitializeHardware() override;
        virtual bool CheckAudioDeviceChange() override;
        virtual bool TeardownHardware() override;
        virtual bool IsInitialized() const override;
        virtual bool GetNumOutputDevices(uint32& OutNumOutputDevices) override;
        virtual bool GetOutputDeviceInfo(const uint32 InDeviceIndex, FAudioPlatformDeviceInfo& OutInfo) override;
        virtual bool GetDefaultOutputDeviceIndex(uint32& OutDefaultDeviceIndex) const override;
        virtual bool OpenAudioStream(const FAudioMixerOpenStreamParams& Params) override;
        virtual bool CloseAudioStream() override;
        virtual bool StartAudioStream() override;
        virtual bool StopAudioStream() override;
        virtual bool MoveAudioStreamToNewAudioDevice(const FString& InNewDeviceId) override;
        virtual FAudioPlatformDeviceInfo GetPlatformDeviceInfo() const override;
        virtual void SubmitBuffer(const uint8* Buffer) override;
        virtual FString GetDefaultDeviceName() override;
        virtual FAudioPlatformSettings GetPlatformSettings() const override;
        virtual int32 GetNumFrames(const int32 InNumReqestedFrames) override;
        virtual void ResumeContext() override;
        virtual void SuspendContext() override;
        
        //~ End IAudioMixerPlatformInterface
        
        static void IncrementSuspendCounter();
        static void DecrementSuspendCounter();
        
    private:
        AudioStreamBasicDescription OutputFormat;
 
        bool    bSuspended;
 
        bool    bInitialized;
        
        bool    bInCallback;
 
        AUGraph     AudioUnitGraph;
        AUNode      OutputNode;
        AudioUnit    OutputUnit;
        uint8*      SubmittedBufferPtr;
        int32 SubmittedBytes = 0;
        
        int32       RemainingBytesInCurrentSubmittedBuffer;
        int32       BytesPerSubmittedBuffer;
        
        double GraphSampleRate;
        
        bool bSupportsBackgroundAudio;
        
        // We may have to grow the circular buffer capacity since Audio Unit callback size is not guaranteed to be constant
        // Currently, this just zero's-out and reallocates, so it will pop. (We always keep largest capacity)
        void GrowCircularBufferIfNeeded(const int32 InNumSamplesPerRenderCallback, const int32 InNumSamplesPerDeviceCallback);
        
        // This buffer is pushed to and popped from in the SubmitBuffer callback.
        // This is required for devices that require frame counts per callback that are not powers of two.
        Audio::TCircularAudioBuffer<int8> CircularOutputBuffer;
        
        int32 NumSamplesPerRenderCallback;
        int32 NumSamplesPerDeviceCallback;
        mutable bool bInternalPlatformSettingsInitialized{ false };
        mutable FAudioPlatformSettings InternalPlatformSettings;
        
        void InterruptContext(bool Interrupted);
 
        bool PerformCallback(AudioBufferList* OutputBufferData);
        void HandleError(const TCHAR* InLogOutput, bool bTeardown = true);
        static OSStatus AudioRenderCallback(void* RefCon, AudioUnitRenderActionFlags* ActionFlags,
                                                          const AudioTimeStamp* TimeStamp, UInt32 BusNumber,
                                                          UInt32 NumFrames, AudioBufferList* IOData);
 
    };
 
}